1. Field of the Invention
This invention relates to a cage for rolling bearing such as ball bearings and roller bearings, and more particularly, it relates to an improvement for cages for retaining rolling elements of rolling bearings.
2. Description of the Prior Art
There are various causes of vibrations and noise in rolling bearing assemblies. However the main cause is considered to be run-out of the cage in a radial direction, with respect to the rolling elements.
Accordingly, in order to reduce such vibrations and noise can be reduced, it is necessary to make the run-out in the radial direction as small as possible. However, this is difficult to achieve with a wave-type cage. As is known to those skilled in the art to which the present invention pertains, a conventional wave-type cage for a ball bearing has an outer race and an inner race with bearing balls interposed between the two races. The bearing, also, comprises a wave-type cage including a pair of wave shaped plates. The plates are assembled by clasping their respective bottoms together to form a plurality of pockets into each of which a ball is received. The balls are spaced apart at an equal pitch in a peripheral direction.
For purposes of illustrating the extent of radial run-out, assume that the radius of curvature of the inner face of a pocket R1a and the center of curvature is positioned on a pitch circle La. Assume, also, that one half of the total axial run-out of the cage, with respect to a ball, is .DELTA.t1a and the radius of the ball is ra. Then, there is a relation .DELTA.t1a=R1a-ra. Assuming that one half of the total run-out of the cage in the radial direction is .DELTA.r1a and the intersecting point of the inner face of the pocket with the radial edge face of the cage is Pa, and further assuming that the line which runs from the point Pa upwardly and normal to the pitch circle intersects the ball at point Qa, then .DELTA.r1a=Pa.multidot.Qa and the value of .DELTA.r1a becomes considerably larger than .DELTA.t1a. In other words, the amount of the run-out of the cage in the radial direction is considerably larger than that in the axial direction.
In order to restrict the radial run-out of the bearing cage, some attempts have been made heretofore, to lessen the extent of its axial movement. However, there have been several drawbacks to this. For example, dimensional errors on the inner surface of the pocket of the cage are liable to be introduced. This can come about from errors in indexing, namely, in circumferentially dividing the pockets and rivet holes; working errors in clasping the two mating regular plates together, and so on. This causes poor lubrication between the balls and the inner face of the cage pockets which results in increased frictional torque, early wear out and/or seizure.
Since some error in the circumferential direction is unavoidable in working, such as, parts making, assembly and so forth, thus the aforesaid value of .DELTA.t1a should be selected taking such errors into account.
Moreover, since there exists a geometric relationship between the .DELTA.r1a and the .DELTA.t1a, the .DELTA.r1a varies as a function of the value of .DELTA.t1a and the amount of r1a is far larger than .DELTA.t1a, any significant effect cannot be expected by reducing the .DELTA.t1a. In other words, reducing .DELTA.t1a is almost non-effective to reduce the extent of the run-out in the radial direction.
The present invention aims to obviate the drawbacks in the cages of the conventional type as mentioned above. Accordingly, an object of the present invention is to provide a bearing cage for retaining the rolling elements having a construction which can readily lessen the run-out of the cage and the rolling elements of a rolling bearing. Another object of the present invention is to provide a bearing which can be operated with less noise and vibrations together with higher service life.